This invention relates to the actuation of microelectromechanical systems devices. In particular, it relates to the actuation or driving of elements in an array in a microelectromechanical systems device.
Microelectromechanical systems (MEMS) devices may include arrays of elements wherein the elements are operable between one or more driven and undriven states by the application of an actuation voltage. Depending on the particular microelectromechanical systems device, the elements may include interferometric modulators (IMODs), switches, Infra Red (IR) detectors, etc.
In some microelectromechanical systems devices, it may be necessary to have multiple arrays, wherein each array comprises only elements of a particular type, and wherein each element type requires a different actuation voltage. An example of such a device is the color IMOD-based display described in U.S. Pat. No. 6,040,937, which includes three sets or arrays of IMODs designed to switch between the colors red/black, green/black and blue/black. Each array of IMODS has a different actuation voltage.
Driving the elements in these multiple arrays between their undriven and driven states present a challenge because different actuation voltages are required.
According to a first aspect of the invention there is provided a microelectromechanical systems device comprising a plurality of elements each having at least two layers disposed in a stacked relationship with a gap therebetween when the element is in an undriven state, the plurality of elements being of at least two different types, each differing in a height of its gap; and a driving mechanism to drive the plurality of elements to a driven state, wherein one of the layers of each element is electrostatically displaced relative to the other layer, and wherein a minimum voltage required to actuate the driving mechanism is substantially the same for each type of element.
According to a second aspect of the invention there is provided a method of fabricating a microelectromechanical systems device comprising constructing an array of elements, each element having a first layer, a second layer spaced from the first layer by a gap when in an undriven state, and an electrode layer to electrostatically drive the second layer to contact the first layer corresponding to a driven state when energized, the elements being of at least two different types which differ in a height of its gap, wherein said constructing includes changing a configuration of each element type to compensate for differences in a voltage required to drive each element to its driven state.
According to a further aspect of the invention, there is provided a microelectromechanical systems device comprising a plurality of elements, each having a first layer, a second layer spaced therefrom by a gap when in an undriven state, and an electrode layer to electrostatically drive the second layer to contact the first layer corresponding to a driven state when energized, the elements being of at least two different kinds, each differing in a height of its gap; and an element driving mechanism comprising an integrated drive circuit having multilevel outputs to energize the electrode layer of each element to cause the element to change from its undriven state to its driven state.
According to yet a further aspect of the invention there is a provided a method for fabricating a microelectromechanical systems device, the method comprising fabricating an array of first elements, each first element conforming to a first geometry; fabricating at least one array of second elements, each second element conforming to a second geometry; wherein fabricating the arrays comprises selecting a defining aspect of each of the first and second geometries based on a defining characteristic of each of the first and second elements; and normalizing differences in an actuation voltage required to actuate each of the first and second elements, wherein the differences are as a result of the selected defining aspect, the defining characteristics of each of the elements being unchanged.